1. Field of Invention
The present invention relates to an electronic device and to a satellite signal reception method for an electronic device that receives satellite signals sent from positioning information satellites such as GPS satellites and acquires current position and time information.
2. Description of Related Art
The Global Positioning System (GPS) for determining the position of a GPS receiver uses GPS satellites that circle the Earth on known orbits, and each GPS satellite has an atomic clock on board. Each GPS satellite therefore keeps the time (referred to below as the GPS time or satellite time information) with extremely high precision. This has led to the development of electronic timepieces that adjust the time kept internally using time information (GPS time information) received from a GPS satellite.
However, because the signals from a GPS satellite are highly directional microwave signals, the satellite signal cannot be received if there is an obstruction between the GPS satellite and the electronic timepiece or other electronic device that receives signals from the satellite. Receiving signals from a GPS satellite is particularly difficult if the electronic device is indoors surrounded by a ceiling and walls, for example.
If the reception process is executed in such an environment, power consumption increases without being able to receive the satellite signal. This is particularly a problem with a battery-powered electronic device such as a wristwatch because battery power is consumed needlessly and the duration time of the battery is thus shortened.
Japanese Unexamined Patent Appl. Pub. JP-A-2008-39565 therefore teaches an electronic device that can prevent needless power consumption by determining whether the electronic device is indoor or outdoor, executing the reception operation if the electronic device is outdoor, and not executing the reception operation if the electronic device is indoor.
The technology taught in JP-A-2008-39565, however, simply decides to execute or not execute the reception operation by deciding if the electronic device is indoor or outdoor, and receiving satellite signals efficiently can be difficult.
More particularly, if the electronic device is a wristwatch that is worn by the user and is determined to be outdoor, the reception operation will execute and continue executing even if the reception environment is actually quite poor because, for example, the user is moving, such as walking through the city, resulting in the orientation of the electronic device changing and the electronic device even moving into the shadow of a building where reception is not possible.